Shock strut



Sept 5, 1944- L; N. cRlsPELL 2,357,505

sHocx sTRUT i l Filed Feb. 27, 1943 INVENTOR.'

Patentedv Sept. 5, 1944 UNITED STATES PATENT ottici-zl snoox s'rRU'r Loren N. Crispell, Kingston, Pa.' v Application February 27, 1943, serial No. 477,427 (o1. 267-64) My invention relates to aircraft landing gears, and has among its objects and advantages the piovision of an improved shock strut embodying telescopic members operating in conjunction with a damping iluid and air compressing means to perform. shock absorbing functions, and in which the strut includes novel meansfor resisting twisting forces transmitted to the strut.

In the accompanying drawing: Figure 1 is a partial longitudinal sectional view of a'strut in accordance with my invention.

Figure 2 is an enlarged'sectional view along the line 2-2 of Figure l, and A Figure 3 is a sectional view along the line 3 3 ofy Figure 2.

In the embodiment of the invention selected for illustration, the strut I comprises a cylinder I2 and a piston member I4 slidable inside the cylinder. A cap I6 is threadedlyconnected at I8 with the upper end of the cylinder I2, and a sealing washer 20 is interposed between the cylinder and the cap to provide a pressure tight condition. This cap is restrained from' accidental rotation by means of set screws 22. Attaching lugs 24 are fixed to the cap I6. Similar attaching lugs 26 are attached to the cap 28 threadedly connected with the lower end of the piston I4, this piston being of tubular formation but having ahead 36 closing its inner end.

A partition 32 is formed integrally with the cylinder I2 and is located intermediateits ends to divide the latter into a iluid containing chamber 34 and an air compressing chamber 36. To the head 30 is iixedly attached a barrell 38 of smaller diameter than the inside diameter of the cylinder I2, `which barrel slides inside an inner cylinder 40 comprising a iiuid and air pressure chamber.

The cylinder 46 is arranged concentrically of the chamber 36 and is ixedto the partition 32. Upon the end 42 of the piston I4 and about the lower end of the barrel 38 is mounted a resilientwasher 44 which is brought into engagement with a second resilient washer 46 attached to the partition 32, such engagement being consummated when the piston I4 is pushed inwardly to the limit ot its stroke. l

In the end 46 of the cylinder 40 is provided a tapered opening or valve seat 50. A valve body 62 of corresponding contour is adapted to lie at rest on the seat 50, but the Lbody may be lifted therefrom in response to air pressure in the chamber 64 of the cylinder 40. A small opening 56 is provided in the body 52 so that the chambers 36 and 54 have limited' communication at all times. Pins 53 are threaded into the end 48 and extend loosely through openings in the body 52, which pins act as guides for the body. The upward movement of the body 52 may be controlled by means of an adjusting screw threaded through the cap I6 and provided with a screw driver slot 62 in its outer end. A lock nut -64 is threadedly connected with the screw 60 and bears against a resilient seal 66 lying in a recess 68 in the cap I6. Thus the screw 60 may be adjusted to diierent positions to vary the air bleeding capacity of the body 52 when the latter is lifted off its seat 50. The cylinder I2 has its lower end formed with an increased diameter for strengthening purposes, since the cylinder I2 is provided with six longitudinal grooves l0 for the reception of splines 'I2 on a tting 'I4 comprising two sections 16,.each embracing 180 degrees of the circumferential area of the piston I4. Grooves 18 are cut longitudinallyxin the piston I4 for the reception of `splines 60 on the sections 16.' The splines 12 restrain the fitting 14 from relative rotation inside the cylinder I2, and the splines 'i8 restrain the piston I4 from relative rotation with respect to the iitting. Thus the piston I4 is telesccpically related to the cylinder I2 for relative longitudinal movement but is restrained from relative rotary motion. The fitting 'I4 is of such length and construction as to amply withstand any twisting or torsional forces transmitted to the parts.

While engagement between the washers 44 and i 46 limit the relative inward movement of the cylinder and the piston. the grooves 16 in the piston I4 terminate short f its end 42, so that the upper end faces of the grooves may have engagement with the fitting I4 to limit the relative extension movement of the cylinder and the piston. Lubricant introducing fittings -82 are attached to the cylinder I2 and pass through the tting I4 for applying lubricant to the piston and the tting.

To the lower end of the cylinder I2 is threadedly connected a collar 64 between which and the lower end of the cylinder is interposed a sealing washer 66.

kThe barrel 36 is Provided with iiuid metering oriiices 36 which extend substantially throughout the full length of the barrel. These orices taper downwardly and place the chambers 34and 54 in communication through the medium of the barrel. A pleated rubber boot or cover is attached to the collar 64 anda collar 62 attached to the piston 4 to provide a closure protecting the collar and that portion of the piston |.4 which has sliding contact with the splined structure.

A iiller pipe 94 is attached to the cylinder I2 and has Acommunication with thechamber 34 adjacent the washer 45. This pipe is provided with a detachable dustproof cap 96. In supplying liquid to the strut, the cylinder and the piston are placed in their fully extended positions, at which time the fluid is poured in up to the level of the pipe 94. While fluid may pass into the chamber 54, the parts are so proportioned that the chamber 54 cannot completely ll with uid, even though `the cylinder l2 and its piston are in their fully telescoped positions. Set screws 98 are threaded through the collar 84 and into the cylinder I2 to hold the collary against accidental displacement.

vThevalve body 52 unseats as the air pressure is increased insidethe chamber 54, thereby permitting rapid compression and slow expansion of air in the chamber 35, since'the air in the chambers 35 when having higher pressure than the air in the chamber 54 can bleed only through the small opening 56 in the valve. This prevents the compressed air in the chamber 36 from causing rebound.

The axle (not shown): may be attached to the piston-I4, as by welding.

Without further elaboration, the foregoing will so fully explain my invention, that others may, by applying current knowledge, readily adapt the same for use under various conditions of service.

I claim:

1. A shock strut comprising a cylinder having ber, a piston slidable in said cylinder and defining one wall of said fluid containing chamber, means restraining the cylinder and said piston from relative rotary movement, a second iluid and air compression cylinder iixedly related to said iirst mentioned cylinder and opening through said partition, valve means for said second cylinder acting to cause a ra/pld iiow of air from the second cylinder into said air compression chamber but a slow iiow from the compression chamber into said second cylinder, and a barrel means xedly related to said piston and slidable in said second cylinder, said barrel means having a passage placing said uid chamber in communication with said second cylinder.

2. The invention described in claim 1 wherein said cylinder and said piston are respectively provided with attaching devices.

,3. The invention described in claim 1 wherein said first mentioned means comprise a band like member interposed between said cylinder and said rpiston, coacting splines on said band like member and said piston, and coacting splines on said band like member and said cylinder.

4. The invention described in claim 1 wherein said .valve means comprise a valve seat in said f second cylinder and a weighted valve body gravitating to a position at rest on said seat and having a small port maintaining continuous communication between said second cylinder and said air chamber, and means for guiding said valve body when lifted off said seat through increased pressure in said second cylinder.

5. The invention described in claim l wherein said valve means comprise a valve seat i n said second cylinder and a weighted valve body gravitating to a position at rest on said seat and having a small port maintaining continuous communication between said second cylinder and said air chamber, means for guiding said valve body when lifted off said seat through increased pressure in said second cylinder, and an adjustable means for limiting the movement of the valve body away from said seat.

6. The invention described in claim 1 wherein a flexible covering is attached to said cylinder and said piston for enclosing that portion of the piston having telescopic engagement with said first mentioned cylinder.

'7. The invention described in claim 1 wherein resilient bumper means are respectively attached to said piston and said partition to limit the movement of said piston inwardly of said first mentioned cylinder.

8. The invention described in claim 1 wherein the passage in said barrel means comprises the tubular formation of the barrel means and a slot in the wall of the barrel means, said slot being of uniform taper toward said piston.

9. The invention describedA in claim 1 wherein said iirst mentioned means comprise two band sections interposed between said piston and said first mentioned cylinder, and coacting splines on said band sections and the piston and the iirst mentioned cylinder. y

l0. The invention described in claim l wherein a filler means is provided for said iiuid chamber adjacent said spartition.

LOREN N. CRISPELL. 

